1. Field of the Invention
This invention relates generally to a shear stress sensor and, more particularly, the invention relates to a dynamic resonant wall shear stress sensor having high bandwidth, high spatial resolution, and high sensitivity capable of fluctuating wall shear stress measurements in all kinds of fluid flows on all kinds of surfaces.
2. Description of the Prior Art
The measurement of unsteady wall shear stress (also called surface shear stress or skin friction) remains one of the great unsolved problems in experimental fluid mechanics. This is in spite of the long history of development of wall shear stress measurement techniques by some of the greatest fluid mechanics and instrumentation experts. Shear stress sensors are required for military, biomedical, and industrial applications as well as for basic understanding of wall-bounded flows. For example, it has been shown computationally that skin-friction drag can be substantially reduced using closed loop control of an actuator with feedback provided by a shear stress sensor capable of fluctuating shear stress measurements. However, no rigorously calibrated wall shear stress sensors with such capabilities exist today.
Although the measurement of wall shear stress has been studied for more than one hundred (100) years, a robust, calibrated sensor capable of measuring fluctuating shear stress is still elusive. Even with new materials and manufacturing processes that have become available over the past fifteen (15) years that enable the fabrication of miniature sensors, the expected improvements have been offset by some of the same problems larger sensors experienced as well as some new difficulties associated with the small sensors.